Add On
May be it helps if some facts become recognized.
At the time of departure it was dark.
RWY 14L is situated to the east of the TWR.
Cowl separation happened on the left side.
With this basics in mind one must consider that ATC had no chance to observe the separation >> darkness >> engine concealed by the fuselage.
Apparently smaller debries were found by succeeding landing or take off.
Then RWY inspection followed by collection of parts and identification.
Only then it was possible and made sense to contact the correct flight.
There are reports that all this took about 45 min., this will take a flight from CGN to PMI into France airspace.
So seen the circumstances: no delay !! Yes may be some amount of luck and yes, someone on the ground might feel not so comfortable anymore.
In genaral it is a shame that every so often one or both of these cowlings start flying by themself!! Looks like the engineering performance on the locking and the lock control mechanism - if available - is not really brilliant !!